Figure 17 shows a young child using a baby walker. The child is standing still. What is the resultant vertical force on the child? Give a reason for your answer.
How to approach this question
1. Recall Newton's First Law. If an object is stationary or moving at a constant velocity, what can you say about the resultant force acting on it?
2. State the value of the resultant force.
3. Explain your answer by referring to the child's state of motion (or lack of acceleration).
Full Answer
Resultant vertical force = 0 N.
Reason: The child is not accelerating (is stationary), so the forces are balanced.
According to Newton's First Law of Motion, an object will remain at rest or in uniform motion in a straight line unless acted upon by a resultant force.
Since the child is standing still, their velocity is constant (at zero) and they are not accelerating. This means the net or resultant force acting on them must be zero. The downward force of their weight is perfectly balanced by the upward forces from the walker and the floor.
Common mistakes
✗ Giving a non-zero value for the force.\n✗ Giving a reason like "gravity is pulling them down" without mentioning the balancing upward forces.
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